Method of making felted sheets



Jan. 5, 1943.

IRON ETC TO WASTE WHITE WATER R. agumN Emu:

,METHQD OF MAKING FELTED SHEETS Filed July 26, 1937 FLOW SHEET CUTTER CUTTER MAGNETIC 5 mm 105' SPIKED-HEAD MILL 41R -CLEANR CUTTER WITH PERFORATED TES FLA

STEAM/N3 CHEST CHEST WHITE WATER MIXING CHEST REFINER SCREENS .PA PER I MACHINE DR/ EELS REJECTS IN V EN TORS ROBERT G. QUINN. HARE) LAB/JON A TTORNEY.

" r of the finished product.

Patented Jan. 5, 1943 grit "ST S P T NT- OFFICE t ;'m.ran sun-rs now-i G. uinn, mum, andflan'y lnrlson. Somervllle, N. 3., asdgnm to Iolms-Hanville Corporation, New York, N. Y.,- a corporation of NewYork Application July :6, m1, sum No. 155,6ll

This invention relates to a felted sheet and the method of making the same. It relates, .particu-- larly, to such a sheet impregnated or adapted to be impregnated with asphalt, pitch, or other composition commonly used in the manufacture of prepared roofing.

The product of the invention is useful for such roofing, for flooring felt, or for. damping the vibration of automobile bodies or the like.

In the making-of felts for these purposes it is customary to use rag fibres mixed with a certain proportion of fibres from old newspapers, commonly referred 'to as news or news stock. The news fibres are relatively inexpensive as compared to the rag. In addition they require less expenditure for power, to put them into condition suitable for felting. However, only a small proportion of news fibres have been used heretofore in satisfactory felts, because of the tendency of a larger proportion of the news fibres to cause slowness in draining water from the fibres inthe felting stage and lack of absorptiveness or porosity It is an object of the present invention to provide an improved method in which rag fibres are these cutters will be in the form ofpieces predominantLv one square lnch or more in area.

The rags are subjected to'ii magnetic separation to remove particles of iron or other magnetic The bits of rags are then sent through a spikedhead mill, to produce a tearing and separation, and then through an air'cleaner, for separating the rag ":stock from buttons, buckles, or other heavy objects not previously removed by magnetic separation. The rags are next passed. through a cutter with perforated plates. These plates are in effect, screens with holes of selected longest dimension, so that the rag fibres, when reduced to a length to pass through the holes, are removed rather i promptly from further action of the cutting mechanism. By proper selection ofthe size of openings in the screen,-there may be passed through made more free (less slow) at the felting stage.

Another object is to provide a method and product in which there may be used a larger proportion of the news stock or other short wood fibres than heretofore, in making a product of satisfactory absorptiveness, strength, tear resistance, and.

general properties for the pu poses mentioned.

Briefly stated, the invention comprises the product resulting from and the method of forming a felt including the rag component thereof in the form of fibres of optimum lengths and, preferably, subjecting the rag fibres to a steaming operation before they are formed into the felted sheet. In another embodiment, the invention includes the steamed rag fibres flted'into a sheet and a saturant impregnated thereinto.

The invention will be illustrated by description in connection with the attached drawing which shows a flow sheet of the preferred embodiment of the method for producing the improved product.

The rags selected are of the kind commonly used for making roofing felts, for example, under the designations grades 1, 2, 3, 4, and 5. In the present method there has been used to'advantage a mixture of grades 1 2, 3, and 4, witha heavy preponderance of grades 2, 3, and 4. Because of the process to be described there may be used the relatively cheap grades of rags, containing fibres that in the conventional beating and felt making steps would become too highly hydrated.

The rags selected are subjected to an operation to cut them into little bits, as by being passed through two conventional cutters arranged in he screen fibres of about thelength that are desired in the finished felt that is to be made. Thus, there have been usedto advantage screens containing closely spaced circular holes varying in different screens between about one-tenth and sne-fourth inch .in diameter. The cutter includes, suitably, a large rotor with'knives mounted lengthwise thereon and an outer casing having a plurality of inwardly extending knives set just to clear the knives on the rotor. The rotor i driven rapidly, say, at a speed of 900 R. -P. M.,

so that there is a draft within the casing which assists in removing the fibres, once they are cut to length to pass through the holes in the screen. Also, the air from-the cleaner, which conveys the rags to the cutter, passes through the cutter-and promotes the removal of the cut fibres of size to pass the restrictions.

All the equipment that has been described, as."

well as that to be described later in performing' "he, method arid manufacturing the product .of the invention, is conventional and is, therefore, not illustrated. For example, the cu ter thathas been described has been used here ofore in the grinding of certain ores.

The cut fibres, having passed through the perforated plates, are subjected to a. treatment to soften the exterior portions thereof without causing hydration throughout the fibres to the extent that is produced by the conventional extended eating operation. Thus, the fibres aresubjected to treatment with hot water or steaming. For instance, they may be immersed for a substantial period, for example, from 15 minutes to several hours in water heated within the range extending from approximately C. to the temperature of. steam at a pressure of 100 to 200 pounds or so to the square inch. The severity (extent of the effect of stearning) is best within about this range of conditions.

The steamed fibres are mixed with a large pro.-

. In this manner there are eliminated extensive beating and also substantial hydration of the fibres subsequent to steaming.

The water which is separated from. the felt on the paper machine, the so-called.wh-ite water, is turned to the process, as, for example, through a white water storage or chest, to the fibres at some stage in advance of the felting operation.

Wood fibres, if used, are introducedsubsequent to the steaming and in advance of the felting operation, as, for instance, into the rag fibres either before they pass through the Jordan or thereafter as shown by the dotted line representing an alternative in the fiow sheet. The wood fibres are separately dispersed, as 'in a pulperlor breaker beater, before being mixed with the rag fibres.

Finally, the felt so formed is dried on a usual paper mill drier, after which it may be wound into rolls for future use or it may be used directly. In case a binder for the fibres is used, the binder is added in fluid form to the stock stream, preferably just before its entry into the refiner.

When the binder composition is inthe form of an emulsion which must be broken to cause adherence of the binder to the fibres, the chemical employed for this purpose is best added after the binder has been thoroughly mixed with the stock, say, after the mixture comes from the refiner.

A binder that may be-used is, an aqueous emulsion of asphalt,wax such as paramn, montan or a mixture thereof, and/or rubber latex. The chemical that is used to break such emulsions and cause separation of the binder on the ,fibres is usually one that changes the acidityof the composition, suitably by decreasing substantially the pH. Thus, there may be used alum, ferric sulphate, or a small amount of a mineral acid. The proportions of binder maybe varied within limits. There may be used say, 5 to 15% of the binder on the total dry weight of fibres, with 1 just su'fiicient of the chemical to cause proper breaking, with the establishment of the pH value, for example, at about 5.2.

For most purposes of the present invention the binder is not necessary and is omitted.

With the omission of the binder, there may be used a relatively large proportion of wood fibres in a mixture with rag fibre, in the production of a satisfactory felt for roofing, flooring, or vibration-damping. Thus, there may be used at least 25 to 40 pounds by weight' of news fibres to 100 pounds of, the felt. The maximum proportion of the news that may be used varies somewhat with the type of the rags selected, the said proportion being larger with the higher grades of rags. The proportion will vary also with the weight of the felt, the proportion that may be: usedbeing larger with the lighter felts and smaller with the heavier felts. The term news" as used herein means repulped waste newspaper,- news pulp or the like.

Since 50-pound felts, that is, felts weighing 50 iesta? tant in the roofing industry, the propertie of such felts will be discussed in detail.

The kerosene value, that"i s,-the; measure of the amount of saturant that may be'absorbed, is satisfactory as is also the Mullen test. Thus, with 25% of wood fibres on the weight of the felt, the kerosene value and the bursting factor of a typicalproduct are not less than 160 and 50%, respectively, by the standard tests. The kerosene value is obtained by immersing the'sheet product in kerosene for one minute, removing the sheet,

allowing it to drip for two minutes, weighing the thus drained material and calculating the increase in weight over that of the original sheet as percentage increase in weight. The bursting fac- 1.01 is determined in usual manner by means. of a Mullen test and calculations therefrom. The bursting factor represents the bursting strength (pounds per square inch) in the Mullen test divided by the weight of the sheet material being tested (in pounds for"430 square feet) multiplied by 100. v

The felt is very free, as determined by testing the fibre stock from which the felt is formed, the fibre stock fed to the machine permitting the rapid flow of water therefron on the paper machine. In a typical run, the rag fibres, when suspended alone in water and tested by the Motschman test, showed a slowness of practically zero, which means that the freeness is nearly infinite. With a news content of 25% or higher, the mixed fibre 'stock has been found to have a slowness of not more than 44 seconds for a Z-gram sampleinches. The bottom of the cylinder is provided with a fine gauze end piece. There is noted the time in seconds required for the water to drain completely through the fibres which become felted on the said gauze, till the outflow becomes discon tinuous.

The bulking value of the felt is relatively low for a given kerosene value, which shows that such pores or spaces as are present within the felt arerelatively accessible to the saturant. It has been found, for instance, that the feltof bulking factor not in excess of 0.12 will have a kerosene value of at least 160. (The bulking fac-v tor is calculated by dividing the thickness of the felt, in liundredths of an inch,'by the weight in pounds of 480 square feet.) 7 As a possible explanation of the combination of desirable properties in the felt, in spite of the high proportion of the inexpensive wood fibres, the screen tests of the rag fibres made as described is of interest.

The rag fibres that have been cut in the cutter with a restricting screen having circular perforations of the preferred diameter of fourteen sixty-fourths of an inch are predominantly within the range of 4-mesh to 28-mesh. Substantially all of the fibres'pass through a '4-mesh screen and all but about a fifthor less by weight are retained on a 28-mesh screen. Of the small pounds for 480 square feet, are: the most imporproportion of material that passes the 28-mesh screen, most of ity is dirt or water-soluble material.

Also, the rag fibres, cut as described, show a half and usually at least two-thirds of their total weightfiner than 4-mesh and coarser than 14- mesh, by which is meant the above proportion of the fibres will pass through a 4-rnesh and be retained on a li-mesh screen, in the Johnson classifier used in establishing the screen test data herein.

On the other hand, nearly all the wood fibres used pass through a l4-mesh screen.

Screen tests on the rag fibres as they come from the cutters and on pulped (defibred) news stock that may be used are as follows: a

In other words, the rag fibres are comparatively long. For this reason there may be used a large proportion of the relatively'fine news fibres, without making the total proportion .of all fibres inthe very fine grades too large for proper freeness during felting and for adequate strength or the finished felt.

A typical mixture of 35 parts by weight of news and 65 of rag fibres showed the following wet screen analysis at various stages in the manufacturing process:

Percentage of total weight Mesh oiscreen Fm At in paper refiner machine Dry Mt In the finished felt, the rag fibre component of this typical mixture will show about the following wet screen test:

Per cent On 4 mes 0 Through 4 and on 8 mesh"- 13 Through 8 and on 14 mesh; 1'1 7 Through 14 and on 28 mesh. 31 Through 28 and on 100 mesh. 20

' Through 100 mesh 19 'Felts so made may-be impregnated with the usual saturants, as, for instance, with 100 to 200 parts of asphalt or pitch to 100 partsdry weight of the felt. as such, they make prepared roofing that is particularly satisfactory in view of its reduced cost.

For best results there may be used, in place of the news stock described, news that has been fractionated by wet screening methods to remove nearly all of the fibres that are so fine as to pass I through a 100-mesh screen, as, for example, news showing 80 per cent or more retained on 100- mesh.

The details, given are for the purpose of lllus-* tration, not restriction, and variations within the spirit of the invention are intended to be included in the scope of the appended claims.

Whatwe claimis:

1. In making a felted sheet, the method whichcomprises cutting rags to pass through a screen having therein closelyspaced holes of largest dimension adapted to pass fibres of the length desired in thefinished product and then promptly removing, through the said holes and away from the cutting mechanism, the rag fibres of such length-as to pass readily through the holes, subjecting the fibres thus formed to water at an ele-- vated temperature within the range of 100 C. to the temperature of steam at 200 pounds per square inch pressure, with preservation of the said length of the fibres, making a dilute aqueous suspension of the thus treated fibres, forming therefrom a felted sheet, and drying the said sheet.

2. In making a felted sheet, the method which comprises cutting rags to pass through a screen having therein closely spaced holes of longest di- 'mension corresponding approximately to the fibre length desired in the-finished product and then promptly removing, through the said holes and away from the cutting mechanism, the rag fibres that are of such length as to pass through the holes, subjecting the 'fibresthus formed to water at an elevated temperature within the range of C. to the temperature of steam at 200 pounds per square inch pressure with preservation of the said length of the fibres making a mixture, in a large volume of water, of the thus.

treated fibres with short wood fibres in proportion that is substantial but, less than the weight of the rag fibres, forming a felted sheet from the said mixture, and drying the said sheet.

3. In making a felted sheet, the method which comprises cutting rags to lengths suitable for felting on a paper machine, subjecting the cut rag fibres to a steaming operation, suspending the steamed fibres in a large volume of water, forming a felt from the suspension, and then drying the felt, the steaming'varying in severity and effect produced between steaming for approximately 15 minutes at about 100 C. and steaming for several hours at temperatures up to those corresponding to steam at a pressure of 200 pounds to the square inch.

aonnar G. QUINN. may LARIBON. 

